published_or_final_version / abstract / Botany / Doctoral / Doctor of Philosophy

Characterization of the determinants of economically important phenotypes showing complex inheritance should lead to more effective use of genetic resources. This study was conducted to determine the number, genome location and effects of QTLs determining malting quality and agronomic traits in the two North American barley quality standards. Using a doubled haploid population of 140 lines from the cross of Harrington x Morex, agronomic phenotype and malting quality data sets from nine and eight environments, respectively, and a 107-marker linkage map, QTL analyses were performed using simple interval mapping and simplified composite interval mapping procedures. Thirty five QTLs were associated either across environments or in individual environments, with five grain and agronomic traits (yield, kernel plumpness, test weight, heading date and plant height). Thirteen QTLs were associated with five malting quality traits (grain protein percentage, soluble/total protein ratio, ��-amylase activity, diastatic power and malt extract percentage). QTLs for multiple traits were coincident. The loci controlling inflorescence type [vrsl on chromosome 2 (2H) and int-c on chromosome 4 (4H)] were coincident with QTLs affecting all traits except heading date and malt extract percentage. The largest effect QTLs -for yield, kernel plumpness test weight, plant height grain protein percentage, S/T ratio, and diastatic power- were coincident with the vrsl locus. QTL analyses were conducted separately for each sub-population (six-rowed and two-rowed). Ten new QTLs were detected in the sub-populations. There were significant interactions between the vrsl and int-c loci for plant height, grain protein percentage, and SIT protein ratio. Positive transgressive segregants were found for all agronomic traits. They were more prevalent in the six-rowed sub-population, indicating that more favorable alleles were fixed in the two-rowed parent. Results suggest that this mating of two parents representing different germplasm groups caused a disruption in the balance of traits involved in malting quality, which resulted in no progeny carrying all favorable alleles and therefore surpassing the quality of either parent. This study describes some of the genetic determinants of agronomic and malting quality traits in a two-rowed x six-rowed cross and it is a first step toward the further characterization and manipulation of these determinants. / Graduation date: 2001